As is common to all breakerless ignition systems of the inductive type, an electronic switch means is provided which allows current to flow in a primary winding and thereafter at a predetermined time an ignition pulse is generated by interrupting the primary current flow. The current interruption results in a sharp collapse of the magnetic field linking the primary coil and thereby an ignition voltage is induced in the secondary winding.
In breaker-point magnetos, the ignition pulse occurs at the same rotational position of the flywheel throughout the speed range. The cam is located so that the points will interrupt the primary current flow at a point along the descending side of the current pulse at low rpm and as the engine speed increases, the ignition point gradually shifts toward the peak of the pulse and thereafter occurs along the ascending side of the pulse. Under the present state of the breakerless ignition art, no means are available for interrupting the primary current flow on the descending slope of the current pulse generated at low rpm in the primary. The triggering of the solid state switching systems invariably takes place at the peak or ascending slope of the primary current and, at increased speeds, the output voltages will consequently be of decreasing value.
Applicant is unaware of any solid state ignition systems which duplicate the ignition timing performance of a breaker-point magneto.
The principal object of this invention is to provide an inductive breakerless ignition system which produces ignition pulses having a timing stability essentially equivalent to that achieved by a breaker-point magneto.
Another object of this invention is to provide an ignition system of the above type having superior timing stability in comparison to breakerless ignition systems heretofore available.
A further object of this invention is to provide a breakerless ignition system of the inductive type wherein the ignition pulse at various engine speeds occurs at essentially the same position of the rotating magnetic field.